1. Field of the Invention
The present invention relates to a radio network controller and a mobile communication system using the radio network controller, and more particularly to improvements in a radio network controller (RNC) in a mobile communication system of a W-CDMA cellular scheme.
2. Description of the Prior Art
FIG. 4 shows an architecture of a W-CDMA communication system that is a mobile communication system. A radio access network (RAN) 1 comprises the radio network controllers (RNC) 4, 5, and a plurality of nodes (Node B) 6 to 9, and is connected via Iu interfaces to a core network (CN) 3 that is a switching network. The nodes (Node B) 6 to 9 mean a logical node for performing the radio transmission and reception, and are more specifically a radio base station apparatus.
An interface between the Node B and the RNC is called Iub, and an Iur interface is also defined as an interface between each RNC. Each Node B covers one or more cells 10, and is connected via a radio interface to a mobile unit (UE) 2. Node B terminates a radio link, and the RNC manages Node B and selects and composes the radio paths at the time of soft hand over. The details of the architecture as shown in FIG. 4 are defined in 3GPP (3rd Generation Partnership Project).
FIG. 5 shows a protocol architecture of the radio interface in the W-CDMA communication system as shown in FIG. 4. As shown in FIG. 5, this protocol architecture comprises three protocol layers, including a physical layer (PHY) 11 denoted as L1, the data link layers 12 to 14 denoted as L2, and a network layer (RRC: Radio Resource Control) 15 denoted as L3.
The data link layer of L2 is divided into three sub-layers, including a MAC (Media Access Control) layer 12, an RLC (Radio Link Control) layer 13, and a BMC (Broadcast/Multicast Control) layer 14. Also, the MAC layer 12 has a MAC-c/sh (common/shared) 121 and a MAC-d (dedicated) 122, and the RLC layer 13 has a plurality of RLCs 131 to 134.
In FIG. 5, ellipses denote service access points (SAP) between layers, or between sub-layers, in which the SAP between the RLC sub-layer 13 and the MAC sub-layer 12 provides a logical channel. That is, the logical channel is provided from the MAC sub-layer 12 to the RLC sub-layer 13, classified according to the function of transmission signal or the logical characteristic, and featured by the contents of transferred information.
Examples of the logical channel include CCCH (Common Control Channel), PCCH (Paging Control Channel), BCCH (Broadcast Control Channel), and CTCH (Common Traffic Channel).
The SAP between the MAC sub-layer 12 and the physical layer 11 provides a transport channel. That is, the transport channel is provided from the physical channel 11 to the MAC sub-layer 12, classified according to the form of transmission, and featured by the kind of information transmitted via the radio interface and the transfer mode.
Examples of the transport channel include PCH (Paging Channel), RACH (Random Access Channel), DCH (Dedicated Channel), BCH (Broadcast Channel), and FACH (Forward Access Channel). The details of the MAC sub-layer 12 and its relationship with the transport channel are disclosed in 3GPP TS25.321 V3.15.0 (2003, 03).
The physical layer 11 and each of the sub-layers 12 to 14 of the data link layer are controlled via a C-SAP providing a control channel on the network layer (RRC) 15. The details of the protocol architecture as shown in FIG. 5 are defined in 3GPP.
Also, in the prior art, there are a C (Control) plane for signaling to transfer the control signal and a U (User) plane for transferring the user data, in which the BMC sub-layer 14 of L2 is only applied to the U plane.